This is a 371 of PCT/EP00/06669 filed Jul. 13, 2000 (International filing date).
The invention relates to an earth conductor for earthing systems, in particular of electrostatic separators, such as dry, semi-dry or wet electrostatic filters, consisting of an electrically conductive core with a plastic or rubber sheath.
Moist, saturated gases are nowadays widely cleaned using wet electrostatic filters, on the precipitation electrodes of which a liquid film forms under the influence of the electric field and runs off continuously. Any particles of dust present are thereby removed as a suspension. If necessary, an additional system of continuously operating mist nozzles can be provided for gas saturation. The moist atmosphere necessitates the use of earth conductors that are good electrical conductors and are made from corrosion resistant materials in order to ensure that the current is safely conducted away from the electrodes. If the earth conductor should be destroyed, the current is conducted away via plastic parts or via the rubber covering of the filter housing, with the result that not insignificant damage occurs, which may lead to the electrostatic filter systems being shut down for extended periods.
DE-C-12 31 216 describes a wet electrostatic separator for cleaning moist chlorine gas or waste gases containing chlorine gas, which, for conducting away the electrical charge of the conductive liquid collecting in the drainage channels, has wick-like, liquid-absorbing cords or ropes produced using a ceramic substance or from glass fibres and connected to an earth conductor.
DE-C-15 57 162 describes a device for the corrosion resistant earthing of precipitation electrodes made from non-conductive material in wet tubular electrostatic dust separators. The lower part of the precipitation electrode tube is rendered electrically conductive by a paint or coating by means of an electrically conductive material and has an earth conductor wound around it in a loop. The strands of the earth conductor in the loop are separated from one another by a spacer made from non-conductive material.
DE-A-43 28 438 discloses an earth conductor for earthing systems of electrostatic separators which has a core made from carbon, e.g. graphite cords, which is encased with a layer of plastic or rubber and which is said to have high corrosion resistance over long operating periods. On use of earth conductors of this typexe2x80x94even in the case of a reduced pressure prevailing in the housing of the electrostatic filterxe2x80x94the capillary action of the earth conductor means that liquid is drawn out of the housing of the electrostatic filter to the screw connections attaching the earth conductor to the earthing system, where it causes considerable corrosion, which leads to destruction of the screw connections with increasing operating time and thus to damage to and shutdown of the electrostatic separator.
The object of the present invention is to provide an earth conductor for earthing systems, in particular of electrostatic separators, which is simple to install, which is flexible and chemically resistant, and which prevents escape of liquid from the housing of the electrostatic separator so that corrosion of the contact zone between the earth conductor and the earthing system does not occur.
The use of the earth conductor according to the invention is particularly suitable for tubular electrostatic filters, which consist of a housing with plastic tubes arranged in parallel and vertically therein, with electrodes running in the centre of each tube, each tube being connected at both ends to the corresponding current-side conductor part of the earth conductor.